In the dyeing of nylon fibers, it is common practice to use acid dyestuffs. However, in most cases the acid dyestuffs now employed suffer from the disadvantage that they have only poor or marginal washfastness. Under these circumstances the dyeings produced must necessarily be given an after-treatment with a fixing agent in order to obtain an acceptable degree of washfastness. The art has, therefore, been confronted with the problem of finding dyestuffs which show substantial washfastness on nylon fibers without the necessity of an after-treatment with a fixing agent. Compounds similar to those claimed herein are those as disclosed in Boll. Sci. Fac. Chem. Ind. Bologna 1969, 27(4) 305-12; as shown by Chem. Abs. Vol.73, 1970 (4920e). Structurally, those compounds differ in at least one respect from those of the instant invention, in that the prior art compounds do not possess an alkoxy substituent. The compounds of this invention have, among other properties, a better solubility in an aqueous dyebath. Also, other known compounds (C.I. Acid Red 104, 116, 148, 177) which are similar to the compounds of this invention are also considerably less soluble in an aqueous dyebath. In addition, a dye similar to dyes of this invention wherein D is a benzylaminophenyl group is commercially available. This particular dye is one in which R.sub.2 is ethyl, R.sub.3 and A.sub.2 are hydrogen, and A.sub.1 and B.sub.1 are methoxy, and B.sub.2 is methyl. However, the particular dye of this invention similar to this known dye shows surprising and unexpected advantages in having a substantially better light fastness, as well as showing a good washfastness.